Porphyroclasts have been widely used to determine the shear sense, vorticity and other kinematic parameters of shear zones. Previous studies have revealed that several factors affect the rotation angle of porphyroclasts. These studies mostly regard porphyroclasts as rigid objects or viscous deformable objects to simulate porphyroclast rotation in the upper or lower crust. However, research on how these porphyroclasts behave in the brittle-viscous transition zone is still limited.

In this study, a two-dimensional viscoelastic finite element model is presented to simulate the rotation and deformation of an elastic porphyroclast embedded in a viscoelastic matrix with various mechanical parameters (Young's modulus, Poisson's ratio and viscosity coefficient) and different boundary conditions (load magnitude and load time). The modelling results demonstrate that the rotation angle of the porphyroclast is strongly influenced by the Young's modulus, Poisson's ratio and viscosity coefficient of the matrix and boundary conditions. The modelling results have a level of consistency with the natural examples of porphyroclast-matrix systems of the Taili and Tianhuang ductile shear zones of the North China Craton. These results are helpful to further explain the rotation and deformation mechanism of porphyroclasts in the brittle-viscous transition zone.

卟啉弹性体已被广泛用于确定剪切带的剪切感，涡度和其他运动学参数。先前的研究表明，几个因素会影响卟啉的旋转角度。这些研究大多将卟啉为刚性物体或粘性可变形物体，以模拟卟啉在上地壳或下地壳中的旋转。然而，关于这些卟啉类在脆性-粘性过渡区中的行为方式的研究仍然很有限。

在这项研究中，提出了二维粘弹性有限元模型，以模拟具有不同力学参数（杨氏模量，泊松比和粘度系数）和不同边界条件（载荷大小）的粘弹性基质中嵌入的卟啉弹性体的旋转和变形。和加载时间）。建模结果表明，卟啉的旋转角度受到基质的杨氏模量，泊松比和粘度系数以及边界条件的强烈影响。模拟结果与华北克拉通的泰里和天煌延性剪切带的卟啉-基质体系的自然实例具有一定程度的一致性。